Hereditary hemochromatosis is a disease of unknown etiology, characterized by excess iron absorption by the intestine, resulting in subsequent parenchymal tissue iron deposition. Three lines of investigation are proposed with the ultimate aim of isolating and characterizing the gene responsible for hemochromatosis. Previous studies have mapped the hemochromatosis gene to a portion of the HLA locus on chromosome six. It is proposed first to characterize this region by pulsed-field gel electrophoresis and hybridization analysis to confirm its actual size and to map specific restriction endonuclease sites. The second phase of this proposal entails searching for DNA restriction fragment length polymorphisms associated with the hemochromatosis gene in several local pedigrees. Initially three well-characterized HLA hybridization probes will be used but further analysis will probably necessitate screening a genomic library to locate other DNA sequences from this region to use as probes. The third line of investigation focuses on a candidate molecule, ferritin, with an established role in iron storage. These studies will entail both protein and RNA characterization. The expression and metabolism of ferritin protein subunits in normal and hemochromatotic lymphocytes and monocytes in culture, following biosynthetic radiolabeling and immunoprecipitation, will be examined. Ferritin-encoding mRNAs will be quantitated by northern blot analysis and the 5' regions of these RNAs characterized by primer extension. Ferritin RNA from intestine, a candidate tissue for the defect in hemochromatosis, will be analyzed by northern blot analysis.